Semiconductor fabrication generally involves numerous sophisticated and complex processing steps. Monitoring and evaluation of each process step is crucial to ensure the manufacturing accuracy and to ultimately achieve the desired performance of a finished device. Throughout numerous processes, such as the imaging process, deposition and growth process, etching and masking process, it is critical, for example, that temperature, gas flow, vacuum pressure, gas chemistry or plasma composition and exposure distance be carefully controlled during each step. Careful attention to the various processing conditions involved in each step is a requirement of optimal semiconductor or thin film processes. Any deviation from optimal processing conditions may cause the ensuing integrated circuit or device to perform at a substandard level or, worse yet, fail completely.
Within a processing chamber, processing conditions can vary. The variations in processing conditions such as temperature, gas flow rate and/or gas composition greatly affect the formation and thus the performance of the integrated circuit. Using a substrate-like device to measure the processing conditions that is of the same or similar material as the integrated circuit or other device provides the most accurate measure of the conditions because the thermal conductivity of the substrate is the same as the actual circuits that will be processed. Gradients and variations exist throughout the chamber for virtually all processing conditions. These gradients therefore also exist across the surface of a substrate. In order to precisely control processing conditions at the substrate, it is critical that measurements be taken upon the substrate and that the readings are available to an automated control system or operator so that the optimization of the chamber processing conditions can be readily achieved. Processing conditions include parameters used to control semiconductor or other device manufacture or conditions a manufacturer would desire to monitor.
Low profile wireless measuring devices are typically mounted on the substrate to measure the processing conditions. For a low profile wireless measuring device to work in a high temperature environment (e.g., temperatures greater than about 150° C.), certain key components of the device, such as thin batteries and microprocessors, must be able to function when the device is exposed to the high temperature environment. In general, the back AR coating (BARC) process operates at 250° C.; a PVD process may operate at about 300° C. and a CVD process may operate at a temperature of about 500° C. Unfortunately, batteries and microprocessors suitable for being used with the measuring devices cannot withstand temperature above 150° C. In addition, the measuring devices may be used for measurement in an operational plasma processing environment. These devices may be exposed to harsh conditions such as excessive temperatures, corrosive chemicals, and bombardment by high energy ions, and high levels of electromagnetic and other radiative noise. Thus, it is desirable to have shielding that may block electrostatic fields and electromagnetic fields from interference with the signals from the measuring devices.
An additional challenge faced by such measuring devices is minimization of the device profile. Such devices should keep a profile of 5 mm or less above the top surface of the substrate in order to fit into various process chambers.
It is within this context that embodiments of the present invention arise.